1. Field of the Invention
The invention relates generally to electromagnetic relays and more particularly to wash-tight electomagnetic relays housed within an inert atmosphere.
2. Description of the Prior Art
In the past, electromagnetic relays have been enclosed within a housing which included an atmosphere containing air. A problem was created because the air included a plurality of gases which contaminated the inner atmosphere of the relay by causing oxidation of the relay electrical components. In order to eliminate the entry of air into the relay housing, a method in the prior art was developed to seal the relay housing. The method included sealing the housing by pouring a self-setting artificial resin onto a base of the relay housing for sealing each penetration through the housing base and sealing the interfacing seam between the relay housing and the housing base. Although air was prevented from entering the relay housing, a new problem was created in that the self-setting aftificial resin produced additional gases. The additional gases also contaminated the inner atmosphere of the relay housing again resulting in oxidation of the relay electrical components.
One attempt in the prior art to solve these problems was disclosed in the German Published Patent Application (DE-OS) No. 26 18 492. The application (DE-OS) No. 26 18 492 discloses a relay having a baseplate which is overlapped by a rim portion of a relay cover. The relay cover is provided with a hump formed in the shell of the relay cover which points in the outward direction. The hump includes a central vent hole for the release of the plurality of gases from inside the relay housing. The sealing of the disclosed relay is effected with the aid for a fleece placed over the baseplate and the lower rim portion of the relay cover. The fleece includes a hole or recess through which the hump is permitted to project. The fleece and the area immediately around the hole or recess is saturated with a curable sealing compound. The central vent hole permits effecting a pressure compensation in the relay during the curing stage of the sealing compound. Subsequent to the curing stage, the central vent hole may be sealed with a viscous resin or adhesive.
A second attempt in the prior art to solve the problem of contamination of the inner relay atmosphere was disclosed in European Patent Application No. 0053870. Application No. 0053870 also discloses a relay having a vent hole to release the plurality of gases from inside the relay housing. The method of sealing is similar to that of Application (DE-OS) No. 26 18 492 except that a fleece saturated in sealing compound is not used. The vent hole in both cited applications is surrounded on the outside of the relay by an extended region for receiving the curable sealing compound. Both applications cited disclose employing the self-setting or hardening (duroplastic) artificial resin to seal the vent hole subsequent to curing the sealing compound. Thus, the additional gases produced by the self-setting artificial resin continue to contaminate the inner atmosphere of the relay.